The Bofors Gun
was a 40mm light anti-aircraft
automatic gun developed by A.B. Bofors of Sweden
and sold to many countries.
It was adopted as a standard AAA gun by the British Army in 1938 and by the US Army in 1941. The German Army also used a small number captured from France and Poland during World War II.
The Bofors fired a 2lb. explosive shell at a muzzle velocity of 2,800ft./sec. at 120 rounds per minute. The maximum ceiling was listed as 23,600 feet but a more practical number was more like 12,500.
The standard mounting was a four-wheeled trailer unit with a gimballed turret and ammunition storage onboard, but some guns were mounted in vehicles as mobile defense for supply and troop convoys.